Mechanical properties calcium carbonate reinforcement

Reinforcing fillers (active) Fumed Silica (Si02) precipitated calcium carbonate (CaCOi) carbon black Thixotropic reinforcing agents (non-slump), adjustment of mechanical properties (cohesion) provide toughness to the elastomer as opposed to brittle materials. 

Non-reinforcing fillers (passive) Ground calcium carbonate (CaCO ) Reduce formulation cost adjust rheology, and mechanical properties. 

Janes, Neumann and Sethna ° reviewed the general subject of solid lubricant composites in polymers and metals. They pointed out that the reduction in mechanical properties with higher concentrations of solid lubricant can be offset by the use of fibre reinforcement. Glass fibre is probably the most commonly used reinforcing fibre, with carbon fibre as a second choice. Metal and ceramic fibres have been used experimentally to reinforce polymers, but have not apparently been used commercially. To some extent powders such as bronze, lead, silica, alumina, titanium oxide or calcium carbonate can be used to improve compressive modulus, hardness and wear rate. 

Methods of fdler pretreatment choice of carbon black for conductive appheations is crucial because impurities on carbon black may have an adverse effect on mechanical properties aluminum oxide and calcium carbonate were coated by a hydrophobic layer of PDMS heat treatment of fumed sihca reduces its ability to reinforce polymer, especially in temperatures above 2OO C ... 

Solid additives in the shape of spheres, cubes, or platelets generally act as a filler (extender) and, with the exception of raising stiffness, do not Improve the mechanical properties of the composite. With very strong adhesive forces between filler surface and polymer chains, however, a filler may also provide reinforcement, for example, carbon black in rubber or uncoated calcium carbonate in polyamides. 

Reinforcements are used to enhance the mechanical properties of a plastic or elastomer. Finely divided silica, carbon black, talc, mica, and calcium carbonate, as well as short fibers of a variety of materials, can be incorporated as particulate fillers. Incorporating large amounts of particulate filler during the making of plastics such as polypropylene and polyethylene can increase their stiffness. The effect is less dramatic when temperature is below the polymer s Tg. 

Since most technical applications require better mechanical properties than those displayed by pure polydimethylsiloxane polymer/crosslinker networks, liquid silicone systems also contain fillers. These are classified as inert, i.e. nonreinforcing, or active, i.e. reinforcing. Inert fillers such as quartz powder, diatomaceous earths, calcium silicates, calcium carbonates, and iron oxides interact neither chemically nor physically with the polydimethylsiloxane netwoflr. They mainly influence the silicone rubber s hardness and swelling properties. 

The curing process takes advantage of the versatile chemical property of silicones. Chemical reactivity is built in the polymer and allows the formation of silicone networks of controlled molecular architectures with specific adhesion properties. The general and inherent molecular properties of the PDMS polymer are conferred to the silicone network. Pure PDMS networks are mechanically weak and do not satisfy the adhesive and cohesive requirements needed for most applications. Incorporation of fillers like silica or calcium carbonate is necessary to reinforce the silicone network (see Composite materials). 

Reinforcing fillers used are carbon black and non-black fillers such as silica, clay, and calcium carbonate although the latter two are used more in lower cost industrial applications and not in tires. Protectant systems consist of antioxidants, antiozo-nants, and waxes. The vulcanization system essentially ensures that the optimum mechanical properties of the polymer system are achieved. Finally, the tire compound can contain various miscellaneous materials such as processing aids and resins. The materials scientist when designing a tire compound formulation has a range of objectives and restrictions within which to operate. Product performance objectives define the initial selection of materials. These materials must not raise environmental concerns, be processable in tire production plants, and be cost effective for the end user [4]. 

Calcium carbonate is heterogeneous nucleating agent, which remains as crystalhne solid upon cooling of the polymer melt, and provides the crystallization sites. A synergistic improvement of mechanical properties of PP was caused by a combination of calcite particles reinforcement and li-nucleation. A distinct Jl-nucleation activity was found with surface-treated calcium carbonate present in PP. ... 

Polypropylene is a very versatile polymer. It has many properties that make it the polymer of choice for various applications (e.g., excellent chemical resistance, good mechanical properties and low cost). There are many ways in which the mechanical properties of polypropylene can be modified to suit a wide variety of end-use applications. Various fillers and reinforcements, such as glass fiber, mica, talc, and calcium carbonate, are typical ingredients that are added to polypropylene resin to attain cost-effective composite mechanical properties. Fibrous materials tend to increase both mechanical and thermal properties, such as tensile strength, flexural strength, flexural modulus, heat deflection temperature, creep resistance, and sometimes impact strength. Fillers, such as talc and calcium carbonate, are often used as extenders to produce a less-costly material. However, some improvement in stiffness and impact can be obtained with these materials. 

A wide range of other reinforcing agents have been used to improve the mechanical properties of polymers. These include clays, calcium carbonate, silica, talc, alumina (see Table 2.6). 

Zhou and co-workers [27] used calcium carbonate as a reinforcing agent for sulfonated PEEK. The calcium carbonate particles were surface treated and the effect of this on the mechanical and thermal properties were determined. The modulus and yield stress of the composites increased with CaCOs particles loadings. This increase was attributed to the bonding between the particles and the PEEK matrix. DSC experiments showed that the particle content and surface properties influenced the Tg and the T of the composites. The Tg increased with the content of fillers while Tn, decreased. The treated fillers were found to give a better combination of properties, which indicated that the sulfonated PEEK played a constructive role in the calcium carbonate/PEEK composites. 

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